In a semiconductor manufacturing process in which various treatments such as, for example, a film formation, are performed on a substrate to be processed (e.g., a semiconductor wafer) in order to form a plurality of semiconductor elements on a surface of the substrate to be processed, a substrate transfer apparatus is used to transfer the substrate to be processed. For example, in a batch type semiconductor manufacturing process, there is a case where a plurality of substrates is transferred at once by a substrate transfer apparatus that is provided with a plurality of substrate carrying plates (see, e.g., FIGS. 16 to 20 in Japanese Patent Laid-Open Publication No. 10-321704). In addition, in a single substrate type semiconductor manufacturing process, there is a case where substrates are transferred one by one by a substrate transfer apparatus (see, e.g., FIG. 21 in Japanese Patent Laid-Open Publication No. 10-321704).
Recently, as the miniaturization and high integration of semiconductor devices have advanced, a problem has been caused by foreign matters generated, for example, on a bevel portion and an edge portion of a semiconductor wafer (substrate) during a manufacturing process of the semiconductor devices. In an effort to remove the foreign matters, a bevel polishing process has been proposed in which the peripheral edge of the substrate is polished using a polishing tape having a surface to which fixed abrasive grains are attached. In the bevel polishing process, in order to remove foreign matters formed on the peripheral edge of the substrate, the polishing tape comes in slide contact with the peripheral edge of the substrate while the substrate is being rotated, thereby removing the foreign matters. For that reason, it is required to accurately position the center of the substrate to be processed at the axial center of a rotary table (stage). Japanese Patent Laid-Open Publication No. 2006-303112 discloses a substrate transfer apparatus to be used in the bevel polishing process.